This invention relates to rocking press machines having rocking shafts that are capable of various swinging motions.
The rocking press machine is a machine that forges metal by means of a combination of a rocking shaft and a metal die. The lower segment of the rocking press comprises a hydraulic press that supports the pressure exerted by the rocking shaft and carries a metal stock to be forged and other devices.
The basic principle of the rocking press machine is to allow the rocking shaft 1 to swing about the central axis thereof with an adjustable angle of eccentricity and an adjustable orbital angular velocity, as shown in FIG. 2. Then, the metal die 2 integral with the rocking shaft 1 swings and thereby forges the metal placed therebelow into a desired shape.
Various swinging motions are attained by varying the angle of eccentricity and orbital angular velocity of the rocking shaft about its own central axis, whereby the metal stock pressed by the metal die 2 is formed into various shapes.
With conventional rocking press machines, the rocking shaft 1 and the metal die 2 therebelow are in one piece. Furthermore, the metal die 2 is shaped like a truncated cone having vertex O at the bottom end thereof, as shown in FIG. 1.
When the working face of the metal die 2 of conventional rocking press machines of this type has line contact with the metal stock or, in other words, the angle of eccentricity xcex8 the central axis of the rocking shaft 1 is equal to the angle of inclination a of the metal die 2 shaped like a truncated cone as shown in FIG. 1, the metal die rolls over the surface of the metal stock about vertex O as the central axis of the rocking shaft 1 moves in orbit.
If the angular velocity of the orbiting central axis of the rocking shaft 1 with respect to the vertical axis is xcfx89 and the angular velocity of the central axis of the metal die 2 rotating on its own axis is xcfx89xe2x80x2 in FIG. 1, the vertical and horizontal components of the angular velocity xcfx89xe2x80x2 are xcfx89xe2x80x2 cos xcex1 and xcfx89xe2x80x2 sin xcex1, respectively.
If the distance between a specific point P of the metal die 2 that is rolling in contact with the metal stock and vertex O is r and the intersection point between a line perpendicular to the horizontal surface at point P and the central axis of the metal die 2 is S in FIG. 1, SP=rcot xcex1.
The orbital speed at point P is xcfx89r.
When the metal die 2 that rolls as described before rotates on its own axis about vertex O, the rotating speed of the horizontal component xcfx89xe2x80x2 sin xcex1 of the angular velocity xcfx89xe2x80x2 at point X and with the orbital speed at point P given above, which can be expressed as SP xcfx89xe2x80x2 sin xcex1=rxcfx89xe2x80x2 cos xcex1 where SP is the radius, is equal to xcfx89r described earlier.
Therefore, equations or xcfx89r=xcfx89xe2x80x2r cos xcex1 and xcfx89xe2x80x2=xcfx89/cos xcex1 hold.
However, the rotation of the metal die on its own axis, resulting from its rolling, produces considerable interference in forming a desired pattern on the metal stock by various swinging motions.
To explain the above fact, FIG. 2 shows a view that is more generalized than FIG. 1. That is, FIG. 2 shows a case in which the angle of eccentricity xcex8 of the central axis of the rocking shaft 1 is not equal to the angle of inclination xcex1 of the metal die 2 or, in other words, the metal die shaped like a truncated cone is not in contact with the surface of the metal stock being worked. Here, a normal line extending from point P on the surface of the conically shaped lower part of the metal die intersects the central axis thereof at point Q, and OQ=a and PQ=b. (Unlike FIG. 1, FIG. 2 shows a case in which the conically shaped part of the metal die is away from the horizontal plane.)
When the metal die rotates on its own axis, point P will become separated from the surface of the metal stock in some instances. Pxe2x80x2 and Qxe2x80x2 in FIGS. 2 and 3 are projections of points P and Q on the abscissa and ordinate in a horizontal plane centered at vertex O. OPxe2x80x2 and OQ can be expressed as follows:
OQxe2x80x2=a sin xcex8(t) and Pxe2x80x2Qxe2x80x2=b cos xcex8(t)
(A functional form xcex8(t) is used because xcex8 can change with time.)
In FIG. 2, point Q rotates about a vertical line passing through vertex O with angular velocity xcfx89, whereas point P rotates not only about the same vertical line passing, through vertex O with angular velocity xcfx89 but also in the opposite direction about a vertical line passing through point Q with an angular velocity equal to the vertical component of angular velocity xcfx89xe2x80x2 of the rotation of the rocking shaft on its own central axis.
When xcex8=xcex1, xcfx89xe2x80x2=xcfx89/cos xcex1 as described earlier by reference to FIG. 1. The inclined surface of the metal die shaped like a truncated cone is away from the surface of the metal stock as shown in FIG. 2. However, xcfx89xe2x80x2 is not always equal to xcfx89/cos xcex1 because of the rotation on its own axis due to the inertia effect of the rolling motion.
The vertical component of angular velocity xcfx89xe2x80x2 of the rotation of the rocking shaft on its own central axis is equal to xcfx89xe2x80x2 cos xcex8(t), as is evident from FIG. 2.
Therefore, the velocity of angular motion in the vertical direction at point Q represents a value obtained by deducting the vertical component of angular velocity due to the rotation on its own axis xcfx89xe2x80x2 cos xcex8(t) from angular velocity xcfx89 of the orbiting central axis.
Thus, coordinates x and y of point Pxe2x80x2 in FIG. 3 can be expressed by the following equations:
x=a sin xcex8(t)cos xcfx89t+b cos xcex8(t)cos(xcfx89xe2x88x92xcfx89xe2x80x2 cos xcex8(t))t
y=a sin xcex8(t)sin xcfx89t+b cos xcex8(t)sin(xcfx89xe2x88x92xcfx89xe2x80x2 cos xcex8(t))t
The following equation can be derived from equation (1):
x2+y2=a2+b2+ab sin 2xcex8(t)cos(cosxcex8(t))txe2x80x83xe2x80x83(2)
x2+y2 cannot be kept constant because cos (xe2x88x92xcfx89xe2x80x2 cos xcex8(t)) t in equation (2) changes successively even if xcex8(t) remains constant.
This means that accurate control required in producing a circular motion that is, the most basic motion in swinging motions is impossible to achieve, let alone accurate control to ensure accurate production of more complex spiral or daisy motion.
FIG. 1 shows a condition in which the inclined surface of the metal die rolls in contact with the surface of the metal stock. If it is assumed that the time for point P to start rolling from a condition in which it is in contact with the metal stock being worked and come in contact with the same metal stock again is t0, equation xcfx89xe2x80x2t0=2xcfx80 holds. Then, the angle of rotation of point P in a horizontal plane is xcfx89xe2x80x2t0=2xcfx80cos xcex1. Therefore, it is impossible to hold the surface of the metal stock within an angular limit of 2xcfx80(1xe2x88x92cos xcex1).
Even if an attempt is made to obtain a desired pattern by pressing the surface of the metal stock with point P at intervals of t0, it is impossible to accurately form the desired pattern because of the shift mentioned earlier.
The object of this invention is to provide rocking press machines whose metal dies do not rotate on their own axes by eliminating the shortcomings of conventional rocking press machines whose metal dies rotate on their own axes.
This invention eliminates the shortcomings of conventional rocking press machines described earlier by providing the following improvement:
(1) In a rocking press machine comprising a metal die adapted to swing about a vertex at a lower end thereof and a rocking shaft mounted above the metal die and transmitting a swinging motion to the metal die, with an angle of eccentricity of the central axis thereof and an angular velocity of the orbiting motion thereof being made adjustable, the improvement comprises a friction disk provided between the metal die and rocking shaft, a gyro enclosing the metal die, supports provided outside the gyro, first projections projecting outward from the metal die, first recesses to rotatably support the first projections therein formed in the gyro, second projections projecting inward or outward and second recesses to rotatably support the second projections therein formed in and on one or the other of the gyro and supports with each of a central axes of regions in which the first and second projections respectively fit in the first and second recesses being on a connecting straight line, two such lines passing through the vertex at the lower end of the metal die, and the line connecting the central axes of the first projections and the line connecting the central axes of the second projections being set at an angle in a horizontal plane.
(2) In a rocking press machine comprising a metal die adapted to swing about the vertex at the lower end thereof and a rocking shaft mounted above the metal die and transmitting a swinging motion to the metal die, with the angle of eccentricity of the central axis thereof and the angular velocity of the orbiting motion thereof being made adjustable, the improvement comprises a friction disk provided between the metal die and rocking shaft, an annular frame fastened to the metal die, a gyro enclosing the annular frame, supports provided outside the gyro, first projections projecting inward or outward and first recesses to rotatably support the first projections therein formed in and on one or the other of the annular frame and gyro, second projections projecting inward or outward and second recesses to rotatably support the second projections therein formed in and on one or the other of the gyro and frame, with each of the central axes of regions in which the first and second projections respectively fit in the first and second recesses being on the same straight line, two such lines passing through the vertex at the lower end of the metal die, and the line connecting the central axes of the first projections and the line connecting the central axes of the second projections being set at an angle in a horizontal plane.